1. Field of the Invention
The present invention relates to electronic binoculars, and in particular to leveling an image-indicating field of an ocular unit, inclined by adjusting an inter-pupillary distance between a pair of ocular units of the electronic binoculars.
2. Description of the Related Art
When binoculars are used, the ocular units of the binoculars are moved according to the following methods and the inter-pupillary distance is adjusted: (1) rotating the left ocular unit and the right ocular unit about an axis of the imaging optical device; (2) sliding the left ocular unit and right ocular unit in a direction parallel to a line connecting the ocular optical axis of the left ocular unit and the ocular optical axis of the right ocular unit.
When an observer adjusts an inter-pupillary distance while holding the binoculars described in (1) only one hand is necessary, while for the binoculars described in (2) two hands are always necessary.
In addition, the type (1) binoculars can have a 2-axial rotary system, so that the axis of rotation is independent for the left ocular unit and the right ocular unit, or can have a 1-axial rotary system, so that the axis of rotation of the left and right ocular units is common.
However, electronic binoculars are proposed that are capable of recording image data in a storage medium and further that have the advantage of night vision. The electronic binoculars are generally provided with an optical system, a photographing lens system, an imaging device, and ocular units. The imaging device converts an optical image produced by the optical system to electric signals. The ocular units have image-indicating devices that display the object image according to the electric signals.
The imaging devices, such as CCDs, and the image-indicating devices, such as LCDs, both have a generally rectangular shape. Therefore, when the observer adjusts an inter-pupillary distance of the type (1) binoculars, the image-indicating devices are inclined by the angle of rotation of the ocular units. Therefore, the images indicated on the image-indicating devices are inclined. It is not comfortable for an observer, to observe an object in this situation.
Japanese unexamined patent publication (KOKAI) No. 2001-281555 discloses electronic binoculars provided with ocular units which can be rotated about their respective ocular optical axes in order to level the inclined image-indicating devices, as is known in the art. According to the disclosed binoculars, for binoculars provided with ocular units including rectangular image-indicating devices, leveling the inclined image-indicating devices horizontally, or leveling the inclined images indicated on the image-indicating devices horizontally, can be done by rotating the ocular units to a proper angle.